It is known that the radiation pattern from a transmitting antenna is defined by the antenna and an associated ground plane to which the antenna is coupled. An advantageous arrangement of antenna and ground plane is described in U.S. Pat. No. 6,097,339, hereby incorporated by reference. That reference describes a substrate antenna that includes one or more conductive traces supported on a dielectric substrate. The supporting substrate is mounted offset from and generally perpendicular to a ground plane associated with the device with which the antenna is being used, though the claims do not recite the perpendicular relation. The substrate antenna employs a very thin and compact structure that may be used as an internal antenna for wireless devices.
U.S. Pat. No. 6,097,339 purports to describe advantages in offsetting the substrate that supports the trace from an edge of the ground plane with which the antenna conductive trace resonates. However, such a disposition between the substrate-mounted antenna trace and the ground plane manifest additional problems that are less prevalent when the antenna overlies a major surface of the ground plane, problems that the reference does not address but which are explored below.
It is known that disposing an antenna in close proximity to, or in contact with, a person's body causes coupling to the body that degrades the quality of signals transmitted from and received at the antenna. Coupling between the antenna and a user is drastically reduced with increasing distance. However, this is not seen as a viable option for portable wireless devices because wireless handsets, mobile stations that a user holds in close proximity to his/her head to operate, remain popular. Increasing the handset size is generally not seen as commercially viable, given continuing consumer preferences for smaller portable wireless devices.
What is needed is an antenna for a wireless handset that reduces RF coupling with a user's body. It would be particularly desirable to provide such a solution that does not constrain further size reductions in portable wireless devices.